References of "Burdanov, Artem"
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See detailThree hot-Jupiters on the upper edge of the mass-radius distribution: WASP-177, WASP-181, and WASP-183
Turner, Oliver D.; Anderson, D. R.; Barkaoui, K. et al

in Monthly Notices of the Royal Astronomical Society (2019), 485

We present the discovery of three transiting planets from the WASP survey, two hot-Jupiters: WASP-177 b (˜0.5 M[SUB]Jup[/SUB], ˜1.6 R[SUB]Jup[/SUB]) in a 3.07-d orbit of a V = 12.6 K2 star, WASP-183 b (˜0 ... [more ▼]

We present the discovery of three transiting planets from the WASP survey, two hot-Jupiters: WASP-177 b (˜0.5 M[SUB]Jup[/SUB], ˜1.6 R[SUB]Jup[/SUB]) in a 3.07-d orbit of a V = 12.6 K2 star, WASP-183 b (˜0.5 M[SUB]Jup[/SUB], ˜1.5 R[SUB]Jup[/SUB]) in a 4.11-d orbit of a V = 12.8 G9/K0 star; and one hot-Saturn planet WASP-181 b (˜0.3 M[SUB]Jup[/SUB], ˜1.2 R[SUB]Jup[/SUB]) in a 4.52-d orbit of a V = 12.9 G2 star. Each planet is close to the upper bound of mass-radius space and has a scaled semimajor axis, a/R[SUB]*[/SUB], between 9.6 and 12.1. These lie in the transition between systems that tend to be in orbits that are well aligned with their host-star's spin and those that show a higher dispersion. [less ▲]

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See detailWASP-190b: Tomographic Discovery of a Transiting Hot Jupiter
Temple, L. Y.; Hellier, C.; Almleaky, Y. et al

in Astronomical Journal (2019), 157

We report the discovery of WASP-190b, an exoplanet on a 5.37 day orbit around a mildly evolved F6 IV-V star with V = 11.7, {T}[SUB]eff[/SUB]} = 6400 ± 100 K, M [SUB]*[/SUB] = 1.35 ± 0.05 M [SUB]⊙[/SUB ... [more ▼]

We report the discovery of WASP-190b, an exoplanet on a 5.37 day orbit around a mildly evolved F6 IV-V star with V = 11.7, {T}[SUB]eff[/SUB]} = 6400 ± 100 K, M [SUB]*[/SUB] = 1.35 ± 0.05 M [SUB]⊙[/SUB], and R [SUB]*[/SUB] = 1.6 ± 0.1 R [SUB]⊙[/SUB]. The planet has a radius of R [SUB]P[/SUB] = 1.15 ± 0.09 R [SUB]Jup[/SUB] and a mass of M [SUB]P[/SUB] = 1.0 ± 0.1 M [SUB]Jup[/SUB], making it a mildly inflated hot Jupiter. It is the first hot Jupiter confirmed via Doppler tomography with an orbital period of >5 days. The orbit is also marginally misaligned with respect to the stellar rotation, with λ = 21° ± 6° measured using Doppler tomography. [less ▲]

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See detailDiscovery of three new transiting hot Jupiters: WASP-161 b, WASP-163 b and WASP-170 b
Barkaoui, K.; Burdanov, Artem ULiege; Hellier, C. et al

in Astronomical Journal (2019), 157(2),

We present the discovery by the WASP-South transit survey of three new transiting hot Jupiters, WASP-161 b, WASP-163 b and WASP-170 b. Follow-up radial velocities obtained with the Euler/CORALIE ... [more ▼]

We present the discovery by the WASP-South transit survey of three new transiting hot Jupiters, WASP-161 b, WASP-163 b and WASP-170 b. Follow-up radial velocities obtained with the Euler/CORALIE spectrograph and high-precision transit light curves obtained with the TRAPPIST-North, TRAPPIST-South, SPECULOOS-South, NITES, and Euler telescopes have enabled us to determine the masses and radii for these transiting exoplanets. WASP-161\,b completes an orbit around its $V=11.1$ F6V-type host star in 5.406 days, and has a mass and radius of $2.5\pm 0.2$$M_{Jup}$ and $1.14\pm 0.06$ $R_{Jup}$ respectively. WASP-163\,b has an orbital period of 1.609 days, a mass of $1.9\pm0.2$ $M_{Jup}$, and a radius of $1.2\pm0.1$ $R_{Jup}$. Its host star is a $V=12.5$ G8-type dwarf. WASP-170\,b is on a 2.344 days orbit around a G1V-type star of magnitude $V=12.8$. It has a mass of $1.7\pm0.2$ $M_{Jup}$ and a radius of $1.14\pm0.09$ $R_{Jup}$. Given their irradiations ($\sim10^9$ erg.s$^{-1}$.cm$^{-2}$) and masses, the three new planets sizes are in good agreement with classical structure models of irradiated giant planets. [less ▲]

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See detailNew transiting hot Jupiters discovered by WASP-South, Euler/CORALIE, and TRAPPIST-South
Hellier, Coel; Anderson, D. R.; Bouchy, F. et al

in Monthly Notices of the Royal Astronomical Society (2019), 482

We report the discovery of eight hot-Jupiter exoplanets from the WASP-South transit survey. WASP-144b has a mass of 0.44 M[SUB]Jup[/SUB], a radius of 0.85 R[SUB]Jup[/SUB], and is in a 2.27-d orbit around ... [more ▼]

We report the discovery of eight hot-Jupiter exoplanets from the WASP-South transit survey. WASP-144b has a mass of 0.44 M[SUB]Jup[/SUB], a radius of 0.85 R[SUB]Jup[/SUB], and is in a 2.27-d orbit around a V = 12.9, K2 star which shows a 21-d rotational modulation. WASP-145Ab is a 0.89 M[SUB]Jup[/SUB] planet in a 1.77-d orbit with a grazing transit. The host is a V = 11.5, K2 star with a companion 5 arcsec away and 1.4 mag fainter. WASP-158b is a relatively massive planet at 2.8 M[SUB]Jup[/SUB] with a radius of 1.1 R[SUB]Jup[/SUB] and a 3.66-d orbit. It transits a V = 12.1, F6 star. WASP-159b is a bloated hot Jupiter (1.4 R[SUB]Jup[/SUB] and 0.55 M[SUB]Jup[/SUB]) in a 3.8-d orbit around a V = 12.9, F9 star. WASP-162b is a massive planet in a relatively long and highly eccentric orbit (5.2 M[SUB]Jup[/SUB], P = 9.6 d, e = 0.43). It transits a V = 12.2, K0 star. WASP-168b is a bloated hot Jupiter (0.42 M[SUB]Jup[/SUB]; 1.5 R[SUB]Jup[/SUB]) in a 4.15-d orbit with a grazing transit. The host is a V = 12.1, F9 star. WASP-172b is a bloated hot Jupiter (0.5 M[SUB]Jup[/SUB]; 1.6 R[SUB]Jup[/SUB]) in a 5.48-d orbit around a V = 11.0, F1 star. WASP-173Ab is a massive planet (3.7 M[SUB]Jup[/SUB]) with a 1.2 R[SUB]Jup[/SUB] radius in a circular orbit with a period of 1.39 d. The host is a V = 11.3, G3 star, being the brighter component of the double-star system WDS23366 - 3437, with a companion 6 arcsec away and 0.8 mag fainter. One of the two stars shows a rotational modulation of 7.9 d. [less ▲]

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See detailThe SPECULOOS Southern Observatory Begins its Hunt for Rocky Planets
Jehin, Emmanuel ULiege; Gillon, Michaël ULiege; Queloz, D. et al

in Messenger (2018), 174

The SPECULOOS Southern Observatory (SSO), a new facility of four 1- metre robotic telescopes, began scientific operations at Cerro Paranal on 1 January 2019. The main goal of the SPECULOOS project is to ... [more ▼]

The SPECULOOS Southern Observatory (SSO), a new facility of four 1- metre robotic telescopes, began scientific operations at Cerro Paranal on 1 January 2019. The main goal of the SPECULOOS project is to explore approximately 1000 of the smallest (≤ 0.15 R[SUB]⊙[/SUB]), brightest (K[SUB]mag[/SUB] ≤ 12.5), and nearest (d ≤ 40 pc) very low mass stars and brown dwarfs. It aims to discover transiting temperate terrestrial planets well-suited for detailed atmospheric characterisation with future giant telescopes like ESO’s Extremely Large Telescope (ELT) and the NASA James Webb Telescope (JWST). The SSO is the core facility of SPECULOOS. The exquisite astronomical conditions at Cerro Paranal will enable SPECULOOS to detect exoplanets as small as Mars. Here, we briefly describe SPECULOOS, and present the features and performance of the SSO facility. [less ▲]

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See detailActivity induced variation in spin-orbit angles as derived from Rossiter-McLaughlin measurements
Oshagh, M.; Triaud, A. H. M. J.; Burdanov, Artem ULiege et al

in Astronomy and Astrophysics (2018), 619(150),

One of the most powerful methods used to estimate sky-projected spin-orbit angles of exoplanetary systems is through a spectroscopic transit observation known as the Rossiter-McLaughlin (RM) effect. So ... [more ▼]

One of the most powerful methods used to estimate sky-projected spin-orbit angles of exoplanetary systems is through a spectroscopic transit observation known as the Rossiter-McLaughlin (RM) effect. So far mostly single RM observations have been used to estimate the spin-orbit angle, and thus there have been no studies regarding the variation of estimated spin-orbit angle from transit to transit. Stellar activity can alter the shape of photometric transit light curves and in a similar way they can deform the RM signal. In this paper we discuss several RM observations, obtained using the HARPS spectrograph, of known transiting planets that all transit extremely active stars, and by analyzing them individually we assess the variation in the estimated spin-orbit angle. Our results reveal that the estimated spin-orbit angle can vary significantly (up to 42 degrees) from transit to transit, due to variation in the configuration of stellar active regions over different nights. This finding is almost two times larger than the expected variation predicted from simulations. We could not identify any meaningful correlation between the variation of estimated spin-orbit angles and the stellar magnetic activity indicators. We also investigated two possible approaches to mitigate the stellar activity influence on RM observations. The first strategy was based on obtaining several RM observations and folding them to reduce the stellar activity noise. Our results demonstrated that this is a feasible and robust way to overcome this issue. The second approach is based on acquiring simultaneous high-precision short-cadence photometric transit light curves using TRAPPIST/SPECULOOS telescopes, which provide more information about the stellar active region's properties and allow a better RM modeling. [less ▲]

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See detailWASP-166b: a bloated super-Neptune transiting a V = 9 star
Hellier, Coel; Anderson, D. R.; Triaud, A. H. M. J. et al

E-print/Working paper (2018)

We report the discovery of WASP-166b, a super-Neptune planet with a mass of 0.1 Mjup and a bloated radius of 0.63 Rjup. It transits a V = 9.36, F9V star in a 5.44-d orbit that is aligned with the stellar ... [more ▼]

We report the discovery of WASP-166b, a super-Neptune planet with a mass of 0.1 Mjup and a bloated radius of 0.63 Rjup. It transits a V = 9.36, F9V star in a 5.44-d orbit that is aligned with the stellar rotation (lambda = -3 +/- 5 degrees). WASP-166b appears to be a rare object within the `Neptune desert'. The planet's low surface gravity and bright host star make it a promising target for atmospheric characterisation. There are variations in the radial-velocity measurements that might result from stellar magnetic activity. [less ▲]

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See detailWASP-190b: Tomographic discovery of a transiting hot Jupiter
Temple, L. Y.; Hellier, C.; Anderson, D. R. et al

E-print/Working paper (2018)

We report the discovery of WASP-190b, an exoplanet on a 5.37-day orbit around an inflated F6 IV-V star with T_eff = 6400 $\pm$ 100 K, M$_{*}$ = 1.35 $\pm$ 0.05 M_sun and R$_{*}$ = 1.6 $\pm$ 0.1 R_sun. The ... [more ▼]

We report the discovery of WASP-190b, an exoplanet on a 5.37-day orbit around an inflated F6 IV-V star with T_eff = 6400 $\pm$ 100 K, M$_{*}$ = 1.35 $\pm$ 0.05 M_sun and R$_{*}$ = 1.6 $\pm$ 0.1 R_sun. The planet has a radius of R_p = 1.15 $\pm$ 0.09 R_Jup and a mass of M_p = 1.0 $\pm$ 0.1 M_Jup, making it a mildly inflated hot Jupiter. The orbit is also marginally misaligned with respect to the stellar rotation, with $\lambda$ = 21 $\pm$ 6$^{\circ}$ measured using Doppler tomography. We compare a Rossiter-McLaughlin analysis (involving radial velocity measurements) with the Doppler tomography method, and find that the latter provides a better constraint on $vsini_{*}$ and $\lambda$. [less ▲]

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See detailThe 0.8-4.5$\mu$m broadband transmission spectra of TRAPPIST-1 planets
Ducrot, Elsa ULiege; Sestovic, M.; Morris, B. M. et al

in Astronomical Journal (2018), 156

The TRAPPIST-1 planetary system represents an exceptional opportunity for the atmospheric characterization of temperate terrestrial exoplanets with the upcoming James Webb Space Telescope (JWST ... [more ▼]

The TRAPPIST-1 planetary system represents an exceptional opportunity for the atmospheric characterization of temperate terrestrial exoplanets with the upcoming James Webb Space Telescope (JWST). Assessing the potential impact of stellar contamination on the planets' transit transmission spectra is an essential precursor step to this characterization. Planetary transits themselves can be used to scan the stellar photosphere and to constrain its heterogeneity through transit depth variations in time and wavelength. In this context, we present our analysis of 169 transits observed in the optical from space with K2 and from the ground with the SPECULOOS and Liverpool telescopes. Combining our measured transit depths with literature results gathered in the mid/near-IR with Spitzer/IRAC and HST/WFC3, we construct the broadband transmission spectra of the TRAPPIST-1 planets over the 0.8-4.5 $\mu$m spectral range. While planets b, d, and f spectra show some structures at the 200-300ppm level, the four others are globally flat. Even if we cannot discard their instrumental origins, two scenarios seem to be favored by the data: a stellar photosphere dominated by a few high-latitude giant (cold) spots, or, alternatively, by a few small and hot (3500-4000K) faculae. In both cases, the stellar contamination of the transit transmission spectra is expected to be less dramatic than predicted in recent papers. Nevertheless, based on our results, stellar contamination can still be of comparable or greater order than planetary atmospheric signals at certain wavelengths. Understanding and correcting the effects of stellar heterogeneity therefore appears essential to prepare the exploration of TRAPPIST-1's with JWST. [less ▲]

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See detailDiscovery of WASP-174b: Doppler tomography of a near-grazing transit
Temple, L. Y.; Hellier, C.; Almleaky, Y. et al

in Monthly Notices of the Royal Astronomical Society (2018), 480

We report the discovery and tomographic detection of WASP-174b, a planet with a near-grazing transit on a 4.23-d orbit around a V= 11.9, F6V star with [Fe/H] = 0.09 ± 0.09. The planet is in a moderately ... [more ▼]

We report the discovery and tomographic detection of WASP-174b, a planet with a near-grazing transit on a 4.23-d orbit around a V= 11.9, F6V star with [Fe/H] = 0.09 ± 0.09. The planet is in a moderately misaligned orbit with a sky-projected spin-orbit angle of λ = 31° ± 1°. This is in agreement with the known tendency for orbits around hotter stars to be misaligned. Owing to the grazing transit, the planet's radius is uncertain with a possible range of 0.8-1.8 R[SUB]Jup[/SUB]. The planet's mass has an upper limit of 1.3 M[SUB]Jup[/SUB]. WASP-174 is the faintest hot-Jupiter system so far confirmed by tomographic means. [less ▲]

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See detailWASP-147b, 160Bb, 164b and 165b: two hot Saturns and two Jupiters, including two planets with metal-rich hosts
Lendl, M.; Anderson, D. R.; Bonfanti, Andrea ULiege et al

in Monthly Notices of the Royal Astronomical Society (2018)

We report the discovery of four transiting hot Jupiters, WASP-147, WASP-160B, WASP-164 and WASP-165 from the WASP survey. WASP-147b is a near Saturn-mass (M[SUB]P[/SUB] = 0.28M[SUB]J[/SUB]) object with a ... [more ▼]

We report the discovery of four transiting hot Jupiters, WASP-147, WASP-160B, WASP-164 and WASP-165 from the WASP survey. WASP-147b is a near Saturn-mass (M[SUB]P[/SUB] = 0.28M[SUB]J[/SUB]) object with a radius of 1.11 R[SUB]J[/SUB] orbiting a G4 star with a period of 4.6 d. WASP-160Bb has a mass and radius (M[SUB]p[/SUB] = 0.28 M[SUB]J[/SUB], R[SUB]p[/SUB] = 1.09 R[SUB]J[/SUB]) near-identical to WASP-147b, but is less irradiated, orbiting a metal-rich ([Fe/H][SUB]*[/SUB] = 0.27) K0 star with a period of 3.8 d. WASP-160B is part of a near equal-mass visual binary with an on-sky separation of 28.5 arcsec. WASP-164b is a more massive (M[SUB]P[/SUB] = 2.13 M[SUB]J[/SUB], R[SUB]p[/SUB] = 1.13 R[SUB]J[/SUB]) hot Jupiter, orbiting a G2 star on a close-in (P = 1.8 d), but tidally stable orbit. WASP-165b is a classical (M[SUB]p[/SUB] = 0.66 M[SUB]J[/SUB], R[SUB]P[/SUB] = 1.26 R[SUB]J[/SUB]) hot Jupiter in a 3.5 d period orbit around a metal-rich ([Fe/H][SUB]*[/SUB] = 0.33) star. WASP-147b and WASP-160Bb are promising targets for atmospheric characterization through transmission spectroscopy, while WASP-164b presents a good target for emission spectroscopy. [less ▲]

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See detailNGTS-4b: A sub-Neptune Transiting in the Desert
West, Richard G.; Gillen, Edward; Bayliss, Daniel et al

E-print/Working paper (2018)

We report the discovery of NGTS-4b, a sub-Neptune-sized planet transiting a 13th magnitude K-dwarf in a 1.34d orbit. NGTS-4b has a mass M=$20.6\pm3.0$M_E and radius R=$3.18\pm0.26$R_E, which places it ... [more ▼]

We report the discovery of NGTS-4b, a sub-Neptune-sized planet transiting a 13th magnitude K-dwarf in a 1.34d orbit. NGTS-4b has a mass M=$20.6\pm3.0$M_E and radius R=$3.18\pm0.26$R_E, which places it well within the so-called "Neptunian Desert". The mean density of the planet ($3.45\pm0.95$g/cm^3) is consistent with a composition of 100% H$_2$O or a rocky core with a volatile envelope. NGTS-4b is likely to suffer significant mass loss due to relatively strong EUV/X-ray irradiation. Its survival in the Neptunian desert may be due to an unusually high core mass, or it may have avoided the most intense X-ray irradiation by migrating after the initial activity of its host star had subsided. With a transit depth of $0.13\pm0.02$%, NGTS-4b represents the shallowest transiting system ever discovered from the ground, and is the smallest planet discovered in a wide-field ground-based photometric survey. [less ▲]

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See detailWASP-189b: an ultra-hot Jupiter transiting the bright A star HR 5599 in a polar orbit
Anderson, D. R.; Temple, L. Y.; Nielsen, L. D. et al

E-print/Working paper (2018)

We report the discovery of WASP-189b: an ultra-hot Jupiter in a 2.72-d transiting orbit around the $V = 6.6$ A star WASP-189 (HR 5599). We detected periodic dimmings in the star's lightcurve, first with ... [more ▼]

We report the discovery of WASP-189b: an ultra-hot Jupiter in a 2.72-d transiting orbit around the $V = 6.6$ A star WASP-189 (HR 5599). We detected periodic dimmings in the star's lightcurve, first with the WASP-South survey facility then with the TRAPPIST-South telescope. We confirmed that a planet is the cause of those dimmings via line-profile tomography and radial-velocity measurements using the HARPS and CORALIE spectrographs. Those reveal WASP-189b to be an ultra-hot Jupiter ($M_{\rm P}$ = 2.13 $\pm$ 0.28 $M_{\rm Jup}$; $R_{\rm P}$ = 1.374 $\pm$ 0.082 $R_{\rm Jup}$) in a polar orbit ($\lambda = 89.3 \pm 1.4^\circ$; $\Psi = 90.0 \pm 5.8^\circ$) around a rapidly rotating A6IV-V star ($T_{\rm eff}$ = 8000 $\pm$ 100 K; $v_* \sin i_*$ $\approx$ 100 km\, s$^{-1}$). We calculate a predicted equilibrium temperature of $T_{\rm eql}$ = 2641 $\pm$ 34 K, assuming zero albedo and efficient redistribution, which is the third hottest for the known exoplanets. WASP-189 is the brightest known host of a transiting hot Jupiter and the third-brightest known host of any transiting exoplanet. We note that of the eight hot-Jupiter systems with $T_{\rm eff}$ $>$ 7000 K, seven have strongly misaligned orbits, and two of the three systems with $T_{\rm eff}$ $\geq$ 8000 K have polar orbits (the third is aligned). [less ▲]

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See detailA low-density hot Jupiter in a near-aligned, 4.5-day orbit around a $V$ = 10.8, F5V star
Anderson, D. R.; Bouchy, F.; Brown, D. J. A. et al

E-print/Working paper (2018)

We report the independent discovery and characterisation of a hot Jupiter in a 4.5-d, transiting orbit around the star TYC 7282-1298-1 ($V$ = 10.8, F5V). The planet has been pursued by the NGTS team as ... [more ▼]

We report the independent discovery and characterisation of a hot Jupiter in a 4.5-d, transiting orbit around the star TYC 7282-1298-1 ($V$ = 10.8, F5V). The planet has been pursued by the NGTS team as NGTS-2b and by ourselves as WASP-179b. We characterised the system using a combination of photometry from WASP-South and TRAPPIST-South, and spectra from CORALIE (around the orbit) and HARPS (through the transit). We find the planet's orbit to be nearly aligned with its star's spin. From a detection of the Rossiter-McLaughlin effect, we measure a projected stellar obliquity of $\lambda = -19 \pm 6^\circ$. From line-profile tomography of the same spectra, we measure $\lambda = -11 \pm 5^\circ$. We find the planet to have a low density ($M_{\rm P}$ = 0.67 $\pm$ 0.09 $M_{\rm Jup}$, $R_{\rm P}$ = 1.54 $\pm$ 0.06 $R_{\rm Jup}$), which, along with its moderately bright host star, makes it a good target for transmission spectroscopy. We find a lower stellar mass ($M_*$ = $1.30 \pm 0.07$ $M_\odot$) than reported by the NGTS team ($M_*$ = $1.64 \pm 0.21$ $M_\odot$), though the difference is only $1.5$ $\sigma$. [less ▲]

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See detailKPS-1b: The First Transiting Exoplanet Discovered Using an Amateur Astronomerʼs Wide-field CCD Data
Burdanov, Artem ULiege; Gillon, Michaël ULiege

in Publications of the Astronomical Society of the Pacific (2018), 130(989),

We report the discovery of the transiting hot Jupiter KPS-1b. This exoplanet orbits a V=13.0 K1-type main-sequence star every 1.7~days, has a mass of 1.090 Mjup and a radius of 1.03 Rjup. The discovery ... [more ▼]

We report the discovery of the transiting hot Jupiter KPS-1b. This exoplanet orbits a V=13.0 K1-type main-sequence star every 1.7~days, has a mass of 1.090 Mjup and a radius of 1.03 Rjup. The discovery was made by the prototype Kourovka Planet Search (KPS) project, which used wide-field CCD data gathered by an amateur astronomer using readily available and relatively affordable equipment. Here we describe the equipment and observing technique used for the discovery of KPS-1b, its characterization with spectroscopic observations by the SOPHIE spectrograph and with high-precision photometry obtained with 1-m class telescopes. We also outline the KPS project evolution into the Galactic Plane eXoplanet survey (GPX). The discovery of KPS-1b represents a new major step of the contribution of amateur astronomers to the burgeoning field of exoplanetology. [less ▲]

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See detailThe First Post-Kepler Brightness Dips of KIC 8462852
Boyajian, Tabetha S.; Alonso, Roi; Ammerman, Alex et al

in Astrophysical Journal. Letters (2018), 853(1), 14

We present a photometric detection of the first brightness dips of the unique variable star KIC 8462852 since the end of the Kepler space mission in 2013 May. Our regular photometric surveillance started ... [more ▼]

We present a photometric detection of the first brightness dips of the unique variable star KIC 8462852 since the end of the Kepler space mission in 2013 May. Our regular photometric surveillance started in 2015 October, and a sequence of dipping began in 2017 May continuing on through the end of 2017, when the star was no longer visible from Earth. We distinguish four main 1%-2.5% dips, named “Elsie,” “Celeste,” “Skara Brae,” and “Angkor,” which persist on timescales from several days to weeks. Our main results so far are as follows: (i) there are no apparent changes of the stellar spectrum or polarization during the dips and (ii) the multiband photometry of the dips shows differential reddening favoring non-gray extinction. Therefore, our data are inconsistent with dip models that invoke optically thick material, but rather they are in-line with predictions for an occulter consisting primarily of ordinary dust, where much of the material must be optically thin with a size scale ≪1 μm, and may also be consistent with models invoking variations intrinsic to the stellar photosphere. Notably, our data do not place constraints on the color of the longer-term “secular” dimming, which may be caused by independent processes, or probe different regimes of a single process. [less ▲]

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See detailThe First Post-Kepler Brightness Dips of KIC 8462852
Boyajian, Tabetha S.; Alonso, Roi; Ammerman, Alex et al

E-print/Working paper (2018)

We present a photometric detection of the first brightness dips of the unique variable star KIC 8462852 since the end of the Kepler space mission in 2013 May. Our regular photometric surveillance started ... [more ▼]

We present a photometric detection of the first brightness dips of the unique variable star KIC 8462852 since the end of the Kepler space mission in 2013 May. Our regular photometric surveillance started in October 2015, and a sequence of dipping began in 2017 May continuing on through the end of 2017, when the star was no longer visible from Earth. We distinguish four main 1-2.5% dips, named "Elsie," "Celeste," "Skara Brae," and "Angkor", which persist on timescales from several days to weeks. Our main results so far are: (i) there are no apparent changes of the stellar spectrum or polarization during the dips; (ii) the multiband photometry of the dips shows differential reddening favoring non-grey extinction. Therefore, our data are inconsistent with dip models that invoke optically thick material, but rather they are in-line with predictions for an occulter consisting primarily of ordinary dust, where much of the material must be optically thin with a size scale <<1um, and may also be consistent with models invoking variations intrinsic to the stellar photosphere. Notably, our data do not place constraints on the color of the longer-term "secular" dimming, which may be caused by independent processes, or probe different regimes of a single process. [less ▲]

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See detailStellar parameters for TRAPPIST-1
Van Grootel, Valérie ULiege; Silva Fernandes, Catarina ULiege; Gillon, Michaël ULiege et al

in Astrophysical Journal (2018), 853

TRAPPIST-1 is an ultracool dwarf star transited by seven Earth-sized planets, for which thorough characterization of atmospheric properties, surface conditions encompassing habitability and internal ... [more ▼]

TRAPPIST-1 is an ultracool dwarf star transited by seven Earth-sized planets, for which thorough characterization of atmospheric properties, surface conditions encompassing habitability and internal compositions is possible with current and next generation telescopes. Accurate modeling of the star is essential to achieve this goal. We aim to obtain updated stellar parameters for TRAPPIST- 1 based on new measurements and evolutionary models, compared to those used in discovery studies. We present a new measurement for the parallax of TRAPPIST-1, 82.4 $\pm$ 0.8 mas, based on 188 epochs of observations with the TRAPPIST and Liverpool Telescopes from 2013 to 2016. This revised parallax yields an updated luminosity of $L_*=(5.22\pm0.19)\times 10^{-4} L_{\odot}$, very close to the previous estimate but almost twice more precise. We next present an updated estimate for TRAPPIST-1 stellar mass, based on two approaches: mass from stellar evolution modeling, and empirical mass derived from dynamical masses of equivalently classified ultracool dwarfs in astrometric binaries. We combine them through a Monte-Carlo approach to derive a semi-empirical estimate for the mass of TRAPPIST-1. We also derive estimate for the radius by combining this mass with stellar density inferred from transits, as well as estimate for the effective temperature from our revised luminosity and radius. Our final results are $M_*=0.089 \pm 0.006 M_{\odot}$, $R_* = 0.121 \pm 0.003 R_{\odot}$, and $T_{\rm eff} =$ 2516 $\pm$ 41 K. Considering the degree to which TRAPPIST-1 system will be scrutinized in coming years, these revised and more precise stellar parameters should be considered when assessing the properties of TRAPPIST-1 planets. [less ▲]

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See detailSPECULOOS Exoplanet Search and Its Prototype on TRAPPIST
Burdanov, Artem ULiege; Delrez, Laetitia; Gillon, Michaël ULiege et al

in Handbook of Exoplanets (2018)

One of the most significant goals of modern science is establishing whether life exists around other suns. The most direct path towards its achievement is the detection and atmospheric characterization of ... [more ▼]

One of the most significant goals of modern science is establishing whether life exists around other suns. The most direct path towards its achievement is the detection and atmospheric characterization of terrestrial exoplanets with potentially habitable surface conditions. The nearest ultracool dwarfs (UCDs), i.e., very-low-mass stars and brown dwarfs with effective temperatures lower than 2700 K, represent a unique opportunity to reach this goal within the next decade. The potential of the transit method for detecting potentially habitable Earth-sized planets around these objects is drastically increased compared to Earth-Sun analogs. A terrestrial planet transiting a nearby UCD could be an exquisite target for a thorough atmospheric characterization, including the search for possible biosignatures, with near-future facilities such as the James Webb Space Telescope. In this chapter, we first describe the physical properties of UCDs as well as the unique potential they offer for the detection of potentially habitable Earth-sized planets suitable for atmospheric characterization. Then, we present the SPECULOOS ground-based transit survey, that will search for Earth-sized planets transiting the nearest UCDs, as well as its prototype survey on the TRAPPIST telescopes. We conclude by discussing the prospects offered by the recent detection by this prototype survey of a system of seven temperate Earth-sized planets transiting a nearby UCD, TRAPPIST-1. [less ▲]

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See detailEarly 2017 observations of TRAPPIST-1 with Spitzer
Delrez, L.; Gillon, Michaël ULiege; Triaud, A. H. M. J. et al

in Monthly Notices of the Royal Astronomical Society (2018), 475(3), 3577-3597

The recently detected TRAPPIST-1 planetary system, with its seven planets transiting a nearby ultracool dwarf star, offers the first opportunity to perform comparative exoplanetology of temperate Earth ... [more ▼]

The recently detected TRAPPIST-1 planetary system, with its seven planets transiting a nearby ultracool dwarf star, offers the first opportunity to perform comparative exoplanetology of temperate Earth-sized worlds. To further advance our understanding of these planets' compositions, energy budgets, and dynamics, we are carrying out an intensive photometric monitoring campaign of their transits with the Spitzer Space Telescope. In this context, we present 60 new transits of the TRAPPIST-1 planets observed with Spitzer/Infrared Array Camera (IRAC) in 2017 February and March. We combine these observations with previously published Spitzer transit photometry and perform a global analysis of the resulting extensive data set. This analysis refines the transit parameters and provides revised values for the planets' physical parameters, notably their radii, using updated properties for the star. As part of our study, we also measure precise transit timings that will be used in a companion paper to refine the planets' masses and compositions using the transit timing variations method. TRAPPIST-1 shows a very low level of low-frequency variability in the IRAC 4.5-μmband, with a photometric RMS of only 0.11 per cent at a 123-s cadence. We do not detect any evidence of a (quasi-)periodic signal related to stellar rotation. We also analyse the transit light curves individually, to search for possible variations in the transit parameters of each planet due to stellar variability, and find that the Spitzer transits of the planets are mostly immune to the effects of stellar variations. These results are encouraging for forthcoming transmission spectroscopy observations of the TRAPPIST-1 planets with the James Webb Space Telescope. © 2018 The Author(s). [less ▲]

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